U.S. Pat. No. 4,736,213 discloses an ink jet printer having a carriage assembly that includes novel nest constructions for insertably positioning a plurality of print/cartridges in accurate vertical interrelations. The nest constructions comprise a knife edge reference surface for cooperating with a detent structure on the print/cartridge orifice plate and indexing means for moving an inserted print/cartridge so that the reference surface and detent structure achieve precise aligning engagement. In one embodiment the indexing means includes camming structures which: (i) force a lower region of the print/cartridge face into contact with the knife-edge, (ii) then move the print/cartridge down until aligning engagement is effected and (iii) then move a bottom portion of the print/cartridge face into proper electrical contact with printer terminals.
While the constructions of the '213 patent perform well, they require fairly accurate motions to assure that the proper engagement occurs between the print/cartridge and printer reference surface. This, in turn, requires accurate fabrication of the indexing parts of the printer nest. Also, the structural approach of the '213 patent results in certain printer nest portions residing in fairly high stress conditions at their indexing position, which, in molded plastic embodiments, can lead to a permanent set in the plastic and loss of their holding force.